#include <iostream>

int main()
{
    std::cout << "please enter numbers to add seperated by a '+'\n"
                  "and end with a zero. for example: 12.6 + 5.4 + 9.2 + 0\n? "  ;

    float sum = 0.0 ;
    float number ;
    char c ;

    while( std::cin >> number && number != 0  && std::cin >> c && c == '+' )
        sum += number ;

    std::cout << "sum is: " << sum << '\n' ;
}